Coronavirus Homeschool Week 3: Plants, Days 1 and 2

This week, I am in charge of the 11AM-1PM interactive educational component of our Coronavirus Homeschool each day. The stormy skies of the last two weeks have made all 3 elementary-school kids itchy with cabin fever. We wanted to do something outdoors now that the sun was poking through the clouds again.

The leaves are unfurling. The flowers are blooming. It's the perfect time to learn about plants (and satisfy NC Core Curricula requirements for multiple grades).

After taking a water sample from my miniature backyard pond (for once, the water was far less green than I'd hoped), I began our Plants rotation with the following 5-minute BBC video about the origin of complex cells and life (we watched to the 1:03 time mark and then fast-forwarded and watched from the 2:13 mark to the end):

After the video, we discussed the differences between prokaryotic cells (bubbles that contain DNA and other freely floating stuff) and eukaryotic cells (bubbles that contain bubbles (organelles) containing DNA and other stuff).

Here's what we think we know:

Three- to four- billion years ago, only prokaryotic cells existed, and they existed in hot stagnant water (think slimy puddle in the middle of summer). These prokaryotic bubbles divided and bounced off one another like soap bubbles in a very hot and dirty bath.  Then one day, just like Pac Man, one prokaryotic cell ate another prokaryotic cell, and eukaryotic cells were born. The prokaryotic cell that was eaten (a special cell called a bacterium) wasn’t digested. It continued to live *inside* the other cell and to create enough energy for the two of them. Meanwhile, the larger cell provided a safe (and wet) home for the bacterium. This kind of mutually beneficial existence is called symbiosis. As they grew together, the cells changed to accommodate one another until they could no longer live separately (this process is called endosymbiosis).

But it's not just that one single prokaryote (bacterium) was symbiotically absorbed by another single prokaryote (host cell) a few billion years ago. Prokaryotes started engulfing bacteria and other prokaryotes like crazy. Shoot, even eukaryotes started engulfing prokaryotes (and likely other eukaryotes)! One very special bacterium (purple nonsulfur bacteria, we presume) evolved into "organelles" (or little organs) called mitochondria, which make energy (from oxygen) in every animal and plant cell today.

Around this same time, special prokaryotic cells called cyanobacteria developed the ability to produce energy using the sun’s rays in a chemical process called photosynthesis. This gave the cells the ability to *make* the energy they needed to grow and reproduce, demonstrating the first signs of life. Once engulfed, cyanobacteria evolved into organelles called chloroplasts, which convert sunlight into the energy required by plant (and algae) cells.

We theorize that prokaryotic cells absorbed the bacteria that became mitochondria first, and then these same cells (or a lot of them anyway) absorbed the cyanobacteria that became the chloroplasts in future plant cells. This is why animal cells contain mitochondria but no chloroplasts, while plant cells contain both mitochondria and chloroplasts. (Here's a GREAT reference regarding current findings supporting this broadly accepted theory: https://blogs.scientificamerican.com/artful-amoeba/green-alga-found-to-prey-on-bacteria-bolstering-endosymbiotic-theory/.)

Through this revolutionary process of photosynthesis, cyanobacteria enabled living, pre-plant organisms to leave water and grow on land. What’s more, their way of making food using the sun's rays produced oxygen as a waste product. Without oxygen, living animals would never have evolved, much less survived. We literally breathe cyanobacteria farts to live.

Cyanobacteria are the oldest living things we have discovered; and, incredibly, they still exist in their primitive form today. In fact, these microscopic organisms are found in all types of water (fresh, brackish, and salt). When cyanobacteria occur in large numbers, called a bloom, they clump together to form the slimy matrix we call “blue-green algae” (even though cyanobacteria are not actually algae).  

On Day 1, I allowed two twenty-minute intervals to watch the first few videos on this page (with a 10-minute snack in between - and, let's be honest, during - the clips). I ended my audio-visual presentation with the following light-hearted(ish) animation about how cyanobacteria have enabled plants and all life on Earth to exist. On day two, we watched each of the kids' favorite videos from the day before (reinforcing the previous day's discussions), then watched and discussed the remainder of the videos on this page, and ended again with the video below (which was the kids' favorite).

On both days,The Cyanobacteria Strike Back animation provided a pathway for us to discuss how easily the ecological balance of our planet can be tipped and how important it is for us to ensure that our waterways remain free of excess nutrients (from fertilization, erosion, sedimentation and general pollution) that enable cyanobacteria and algae to thrive (and die) at levels that are toxic to the animals who drink and/or live in that water (including us).

By engulfing cyanobacteria, early eukaryotic cells evolved into all the photosynthetic plants (and algae) in our world. And as plants continued to change and improve, they developed their own special parts. For the active portion of our Day 1 lesson, we reviewed the parts that are common to all plants and played "I spy" in the front yard, each of us taking turns spotting a particular plant part and providing hints while the others located it. Next we pulled up some weeds (there are plenty in my lawn) and examined their leaves, stems and roots. Then we dissected a camellia flower (already on the ground), paying special attention to the anthers and filaments and the combined stamen that they formed.

For the active part of Day 2 (which was delightfully sunny and cool), we planted vegetable seeds in individually labeled plastic containers (1 per child) and seedlings in the backyard garden (1 or more per child).

On both days, we finished the two-hour lesson by listening to (and watching) this fabulous poem that summarizes the evolution of life on Earth (in a mere 1 minute):

The Dr-Seuss-like rhythm and rhyme is paving the way for a future poetry and creative writing lesson :-)

I left the kids with an easy homework assignment - to neatly write the following on lined paper: cyanobacteria = prokaryote; photosynthesis; anther; filament; stamen. On day two, they were to write: mitochondria, cyanobacteria, chloroplast, symbiosis and endosymbiosis. That's it.

Check back to see how we go with day 3 of our CHS (Coronavirus Home School) lessons on Plants and find out more about my writing and educational work at www.melissarooneywriting.com.